Who provides the basic link between hardware and operating system?

Answer 1

Computers are comprised with layers of abstraction. At the very lowest level is voltages, circuits, transistors, and silicon. The next layer above hardware is the operating system. Rather than re-writing code for every type of hardware access over and over again, the OS manages the hardware and provides "hooks" to use it. These hooks, or "interfaces" allow your code to have a common method to access disparate hardware. So using the interfaces provided by the OS, you can write your Application. In each of these layers, there are sub layers, for example, hardware might have firmware--a sort of low-level instruction set that dictates how the hardware should run, stored in EEPROM, and loaded when the drive is powered up. Another sublayer is how a higher level language like python provides a libraries to write network software without having to program directly to the raw socket api provided by the OS. The OS handles most hardware/software interaction. Hardware vendors write "plugins/modules/drivers" which allows the OS to control their specific hardware. So you would write a software Application that takes advantage of these OS provided interfaces to hardware. For example if you wanted to power down the computer, windows provides an interface to shutdown the computer. Your software would call this interface, and upon compilation/interpretation, turned into code that will call an interface for the OS. This interface, in turn will execute a well-known set of instructions to instruct the computer to shut down. These instructions are 0's and 1's, low and high volts, which access a specific part of the computer that is designed to handle powerup/shutdown/standby, and given the right signal, will do just that